1. Technical Field
The disclosure relates to a teeth-whitening gel, specifically a high-molecular teeth-whitening gel without thickeners.
2. Description of Related Art
The teeth-whitening is a popular item in cosmetology. The methods of the teeth-whitening can be simply classified into porcelain veneer, all-ceramic crown, and teeth-bleaching, etc. Though the porcelain veneer and the all-ceramic crown are very effective, their acceptability to customers are constantly limited by the disadvantages such as tending to induce sensitive teeth, need of removal of partial healthy teeth, and high cost. In contrast, because the teeth-bleaching has less impact on dental tissues and lower price, and the improvement of techniques and materials, the teeth-bleaching becomes more and more popular these years.
Since the 19th century, scientists had been starting the research in the teeth-bleaching. In the beginning, a bleaching reagent was used to be applied to the surroundings of the teeth. It allows the reagent to permeate the enamel of the teeth for bleaching. However, the efficiency of this method is limited. Next, other scientists had been trying to dispose a bleaching reagent into the pulp cavity directly, and expecting better performance by bleaching the teeth inside out. In 1961, the Spasser's team proposed a method which included mixing sodium perborate and water to form a gel, disposing the gel into the pulp cavity of teeth, and then removing the gel after 1-2 weeks. However, it was inconvenient that the users needed to keep bleaching their teeth by themselves at home for better teeth-bleaching performance. In 1963, the Nutting and Poe's teams proposed an improved method by simply replacing the water used in Spassers's method with a 30% hydrogen peroxide aqueous solution. However, the decomposition of hydrogen peroxide may release free radicals, and an elevated temperature is required to increase the whitening efficiency (U.S. Pat. Nos. 4,528,180 or 4,687,663).
Most bleaching reagents for teeth-whitening were mixtures containing hydrogen peroxide. Now, the main ingredient of a wide variety of the teeth-whitening products is still hydrogen peroxide or its precursors with additional catalysts, surfactants, preservatives or thickeners, etc. For instance, carbamide peroxide, a key ingredient of common teeth-bleaching reagents, is a precursor of hydrogen peroxide. Carbamide peroxide is also named as urea hydrogen peroxide because it will spontaneously decompose into hydrogen peroxide and urea. When the decomposition occurs, the generated urea will increase the pH value and stabilize the generated hydrogen peroxide, and therefore carbamide peroxide is frequently applied in the extended-wear teeth-bleaching at home. However, the teeth-bleaching efficiency of this method is limited because the conversion rate for carbamide peroxide to hydrogen peroxide is not high enough.
From the prior references, many materials other than the aforementioned are used in the teeth-whitening, e.g., hydrochlorites, organic peroxides, inorganic peroxides, hydroperoxides, and peracids, etc. No matter of sodium perborate, hydrogen peroxide or carbamide peroxide, all these peroxides intrinsically possess a certain oxidizing capabilities for the teeth-whitening. However, such whitening ingredients are small molecules of peroxides with high fluidity that would result in allergy or irritation when contacting oral tissues. Thickeners are required as additives in the teeth-whitening ingredients above mentioned to decrease the fluidity and avoid those problems.
The disclosure aims for solving the forgoing shortcomings of relevant prior arts, and provides an efficient solution to enhance safety and convenience of the teeth-whitening operation.